1. Field of the Invention
The present invention relates to a sterilizable package, and more particularly to a sterilizable pouch for medical and dental instruments, the pouch having an improved seal for closing the pouch.
2. Background of the Art
Medical instruments and supplies used in hospitals, clinics, and private offices of physicians and dentists are transported and/or stored in sterile packaging. Ordinarily, the unsterile device is first inserted into a pouch or envelope. The pouch is then sealed and sterilized.
Two common methods of sterilization are steam sterilization and sterilization with ethylene oxide gas. Both types of sterilization are performed at temperatures above 200.degree. F. and with vacuum cycling. In order to insure sterilization of the medical instrument in the interior of the sealed pouch, at least one side of the pouch is a sheet of porous material such as, for example, a sheet fabricated from spun bonded polyolefin fibers. Such a sheet has a pore size sufficient to allow small molecules (water, ethylene oxide) pass through while blocking the entry of larger entities such as viruses and bacteria. The sealed pouch with medical instruments is placed in a chamber and subjected to cyclic treatment of steam or ethylene oxide alternated with vacuum treatment to remove the sterilizing gasses from inside the pouch. During the vacuum treatment especially, the pouch puffs-up until enough gas has escaped from within the pouch to equalize the internal and external pressures. This puffing-up of the pouch produces severe stress on the bonded areas between the sheets which are joined together to form the pouch.
Some types of pouches completely enclose the medical instrument by means of heat sealing the two sheets that form the pouch. Heat sealing requires special machinery and is generally feasible for use only at the factory.
Disposable instruments are generally packaged and sterilized at the factory. On the other hand, reusable instruments, especially dental instruments, are often sterilized on location at the hospital, clinic, or office. Pouches for enclosing reusable instruments are usually heat sealed at the factory on three sides, but have an open end which is sealed manually with a flap having a pressure sensitive adhesive tape.
U.S. Pat. No. 4,358,015 to Hirsch discloses a sterilizable pouch with a foldover flap having a double coated pressure sensitive adhesive tape affixed thereto. A release liner is provided for easier handling, the release liner having sterilization indicator ink printed on one side. The release liner can be peeled off the tape and inserted into the pouch before the pouch is sealed by the user. One problem is that to accept printing the liner cannot have a non-stick coating on the side on which the ink is to be applied. That is, the printed side of the liner must be adherable. However, if such a tape were rolled for storage the exposed adhesive side would contact the adherable side of the liner, thereby rendering the roll unusable. Therefore, where printed liners are used the roll of tape usually includes a secondary liner with single or double sided non-stick coatings. For example, the secondary liner can be used to cover the exposed pressure sensitive adhesive side of the tape. When the tape is rolled the pressure sensitive adhesive does not contact the printed adherable side of the release liner. The secondary liner is removed by the pouch manufacture to attach the adhesive tape to the foldover flap of the pouch. The release liner with the sterilization indicator is removed by the user prior to sealing the pouch. However, it would be advantageous to eliminate the need for a secondary liner, which represents additional cost.
A further problem with some pouches sealed with pressure sensitive adhesive flaps is "tunneling." That is, after the sterilization has been completed, ripples are sometimes observed on the sealing flaps of the pouches. These ripples can provide potential pathways, i.e., tunnels, for air and microorganisms to access the interior of the pouch. Thus, while sterilization of the interior of the pouch can be assured by certain indicators, continued maintenance of sterile conditions within rippled pouches can be in question.
It would be advantageous to reduce tunneling in pouches having pressure sensitive seals, and thereby insure the integrity of the sealed, sterilized instrument.